In polarization-maintaining areas, such as dispersion compensation modules (DCM), dual-pass amplifiers, 40Gbps high-speed systems, and Raman pump applications, polarization-maintaining Optical Circulator are frequently employed. Polarization-independent optic circulators are commonly employed in high-speed, bidirectional, and dense wavelength division multiplexing (DWDM) systems, along with fiber gratings and other reflecting devices.